454 oil pressure sending unit

[Slooptin]

I'm in the process of doing head gaskets on my 454 and while I'm waiting on parts to arrive, I wanted to fix a problem I'm having with my oil pressure gauge. I don't think it's reading accurately, because with key on/engine off, the gauge shoots up to 30psi and with the engine on, it's pegged at 60. I'm thinking its a bad sending unit because the gauge will full sweep. My truck has the "fat" sending unit on it now, but I'm noticing there are two different styles of sending unit, a "fat" one and a smaller one that looks similar to what's on my jeep 4.0 motor. Both are 1 wire, but I'm wondering if there's a difference in voltage output between the two that might give inaccurate reading

 

[Dave M]

I'm in the process of doing head gaskets on my 454 and while I'm waiting on parts to arrive, I wanted to fix a problem I'm having with my oil pressure gauge. I don't think it's reading accurately, because with key on/engine off, the gauge shoots up to 30psi and with the engine on, it's pegged at 60. I'm thinking its a bad sending unit because the gauge will full sweep. My truck has the "fat" sending unit on it now, but I'm noticing there are two different styles of sending unit, a "fat" one and a smaller one that looks similar to what's on my jeep 4.0 motor. Both are 1 wire, but I'm wondering if there's a difference in voltage output between the two that might give inaccurate reading

The left one is a straight switch for the oil light, the other for gauges. Sounds like a crook sender.

 

[Camar068]

yeh it sucks some websites will get them backwards, or even the guy behind the counter will get it wrong.

With it reading 30 psi w/o the engine running, from my experience, its because someone put teflon tape over the input, very dirty oil, after an oil flush, or a bad signal to the gauge. I bet you could take yours out, spray/flood it with carb or break cleaner and let it sit/drain over night. Over the past 5 years I've changed 3 and 2 were after engine flushes, other was teflon. Worth a shot over a local $30 part.

I didn't change the last one after I did a seafoam flush on the block. The gauge went to 30 w/o engine on initially, but went back down after about 100 miles.

 

[Slooptin]

Awesome, thanks